[The effects of caffeine on the respiratory depression by morphine].
The effects of intravenous administration of caffeine on the discharge of the phrenic nerve were studied following vagotomy in 7 pentobarbital anesthetized mechanically ventilated rats. Morphine (0.4 mg.kg-1.min-1) was administered until the respiratory rate decreased to about half of the baseline respiratory rate. In those state, we first administered caffeine (20 mg.kg-1), intravenously and then administered naloxone (0.02 mg) intravenously. The increase of inspiratory time from 0.49 +/- 0.16 to 2.01 +/- 0.47 s by morphine recovered to 0.86 +/- 0.38 s by caffeine and 0.50 +/- 0.22 s by naloxone. Expiratory time did not change during each drug administration. The decrease of respiratory rate from 46.6 +/- 5.9 to 20.6 +/- 4.1 breaths.min-1 by morphine recovered to 39.6 +/- 6.1 breaths.min-1 by caffeine and 47.6 +/- 4.6 breaths.min-1 by naloxone. Amplitude of integrated phrenic nerve discharge increased to 117 +/- 32% by caffeine and 156 +/- 39% by naloxone compared to the baseline. These results suggest that caffeine acts as a respiratory stimulant on the respiratory depression by morphine.
Kasaba
T
T
Department of Anesthesiology, Miyazaki Medical College.
Takeshita
M
M
Takasaki
M
M
D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D003864:Depression, Chemical; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D012119:Respiration / Q000187:drug effects*; D012131:Respiratory Insufficiency / Q000139:chemically induced* / Q000188:drug therapy
D000701:Analgesics, Opioid; D002110:Caffeine; D009020:Morphine